LIFE HISTORY OF AMCEBA PROTEUS LEIDY. 347 



known as Amoeba guttula (Fig. n), and it is suggested that 

 possibly this creature hitherto accorded specific rank, may be 

 merely a developmental stage in the cycle of proteus. That 

 Amoeba radiosa was named from the radiosa stage of Amoeba 

 proteus has been indicated. The radiosa stage which we have 

 observed in this developmental series may be similar. 



A new type of modification now takes place, as has been said, 

 when the pseudopodia become longer and more spinous. During 

 this stage, in respect to size, configuration, and characteristic 

 spineous, immobile, hyaline, ray-like pseudopodia, the creatures 

 are apparently indistinguishable from the species known as 

 Dactylosph&rium radiosum. Hence we shall term this stage the 

 Dactylosphcerium stage (Fig. 15). 



The genus Dactylosphcerium was established by Hertwig, and 

 Lesser ('74) to receive the organism which they described as 

 Dactylosphcerium vitreum. The species now known as Dactylo- 

 sphcerium radiosum, however, was not referred originally to that 

 genus, but to the genus Amceba, as Amoeba radiosa, by Ehrenberg 

 ('30). It was transferred to the genus Dactylosphcerium by 

 Biitschli ('80), who however erroneously called it Dactylosphceria. 

 Cash ('05) says of it: "The body consists of granular protoplasm 

 and when all the pseudopodia are withdrawn it may become 

 spherical or bluntly lobed ; or it may assume an active amoeboid 

 phase, when it is hardly, if at all, 1 to be distinguished from the 

 smaller forms of Amceba proteus." It occurs in marshes and 

 pools, "less common than Amoeba proteus, with which it is usually 

 associated." 2 



It was observed that not all of the young Amcebce acquired this 

 Dactylosphcerium-\ike form. Some became small radiosa, passed 

 on to large radiosa, and thence on to the proteus form. It seemed 

 to be the usual thing, however, for the majority to assume the 

 form of Dactylosphcerium, and the suggestion is made that perhaps 

 Dactylosphcerium radiosum, like other former species, may be 

 forced to relinquish its specific distinction. 



From the bodies of those individuals which had assumed the 

 Dactylosphcerium form, lobate pseudopodia were occasionally pro- 

 truded, and at length the creature became almost globular, and 



- The italics are the author's. 



